For the past month, I've not been cycling to work. I've been getting in a warm, dry, cosy car instead. I thought it would be a treat, a break from pedalling along wet and cold roads in some of the worst weather of the year – but how wrong I was. The result of driving to work is I'm grumpy and getting even more unfit by the day.

The reason I'm not cycling is because I'm house-sitting for friends and need a car to get back to take the dog out at lunchtime. In the morning, I've been moving sloth-like from the cocoon of my duvet to the snug warmth of the car.

I then sit and drive just under five miles to work, only moving to change gear – I do not break into a sweat and my heart only races through stress, not exertion. When I arrive at work, I park close to the front door, so if I'm lucky I take maybe two or three gulps of fresh air and I'm inside. It's no way to start the day.

I'm not alone in finding it difficult to get started without my dose of fresh air and exercise before work: most teachers will tell you that children who walk or cycle to school are more alert and ready to learn than those who arrive by car. Research completed more than 10 years ago also shows that children who exercise have better concentration and are less disruptive, so maybe this explains why I'm feeling so sluggish not cycling.

Logically, driving is the easy option: it should be the stress-free, easy way to get to work, but let me tell you it is not. Just a few days into my month of driving, I begin to get more and more annoyed by the traffic jams and school run mums and dads clogging the roads.

As the cyclists sail past my window while I'm stuck in a queue, I envy them and can see why drivers on my route get annoyed with me when I'm on my bike – it's not just because I get in the way, it's also because I'm always moving and making progress.

I also thought that by driving, I might get a bit of a lie-in, but that's not happened yet, as I have to have a little flexibility in my journey time just in case there is yet another jam. This means I leave at exactly the same time as when I cycle, so I'm not saving any time and, on top of it all, I'm paying for the privilege by burning expensive petrol.

Before you start thinking I'm an exercise nut, let me set the record straight: I'm not the kind of girl who cycles 40 miles in a headwind dressed head to toe in Lycra just for fun.

You see, the truth is I don't really like exercise – my default mode is to avoid it if I can. This month, without cycling, I've done no real exercise: I feel guilty then try to go to the gym, but riding a stationary bike feels pointless, as there is no incentive for me to climb an imaginary hill. The result is I slack off and take it easier than I would if I was on a real road; and going to the gym costs me two things I can't afford: time and money.

I'll be back on my bike tomorrow, because my friends are back from their holiday. Not cycling has made me realise I ride because it's easier, cheaper and I get a bit of exercise without having to make a big effort. Cycling puts me in a good mood, so I'm better equipped to face a day at work.

I don't drink coffee, but usually I don't need to – it's the wind in my hair and, especially at this time of year, the rain and sleet on my face that really wake me up.

• Victoria Hazael works at the CTC, a national organisation representing cyclists in the UK